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Dang My Appetite! December 8, 2010

Posted by wframe488 in Behavior, Biology, Health, Medicine, Nutrition, Physiology.
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The Biggest Loser

It wasn’t until recently America realized just how overweight people were getting in our country. I believe we are one of the most overweight countries of the world if I am not mistaken. It seems like new diet plans, weight-loss pills, and surgeries are developed everyday to help obese Americans shed those pounds. Weight-loss has definitely been growing its popularity, for example new reality television shows like The Biggest Loser , Weighing In, and Celebrity Fit Club, to name a few, have gotten people interested in getting up off the couch and exercising.

The fast food industry and video games can be partially blamed for helping Americans achieve the great honor of being one of the “biggest” countries in the world, but let’s not forget about our genetics. There are several hormones in our endocrine system that plays a role in weight regulation and weight-related behaviors like hunger and satiation. Two of the most popular and most talked about weight regulating hormones would have to be ghrelin and leptin.  We all typically produce these hormones, but in different amounts depending on the person. Ghrelin is a preprohormone that is normally produced in the stomach. It is a known appetite inducer and has also been known to slow down metabolism and decrease the body’s ability to burn fat. It stimulates the hypothalamus to release growth hormone via a GSH receptor. Leptin, on the other hand, is known to aid in appetite inhibition. It is expressed predominantly by adipocytes and contains highly expressed receptors in the hypothalamus region of the brain. It stimulates the hypothalamus via an Ob receptor to decrease appetite and body weight.

Ghrelin and Leptin Action Summary

One research article that I found about this particular topic, by J.P.H. Wilding, was titled “Food Fails to Suppress Ghrelin Levels in Obese Humans”. This research paper investigated the effects of a test meal on the plasma levels of both ghrelin and leptin. They sampled 13 lean and 10 obese subjects and found that the lean subjects exhibited a decrease in both ghrelin and leptin levels after a meal whereas the obese did not show any signs of decrease in concentration of these two hormones. The paper goes on to explain that the role of the decline in leptin of the lean subjects is unknown, but the lack of suppression following a meal of the obese subjects could lead to increased food consumption. This suggests that ghrelin is involved in the pathophysiology of obesity. This appetite inducing hormone is secreted by our bodies with out our control unfortunately and for those that secrete more will mostly likely tend to be bigger human beings just based off of overall caloric intake.

Food Groups

In regards to dieting, one major problem that almost all people possess after they diet is the regain of weight. This mainly is due to the idea that even though your weight is now maintained at a healthy level your appetite still remains the same as it once was, thanks to these two hormones mentioned previously. One interesting article that I read from the Journal of Clinical Endocrinology and Metabolism, was titled, “Appetite Hormones May Predict Weight Regain After Dieting”, which was by Ana B. Crujeiras. Her colleagues and her evaluated a group of 104 overweight men and women during an 8-week low-calorie diet and again 32 weeks after treatment. The scientists measured body weight and plasma ghrelin and leptin levels before, during, and after dieting. What is interesting about this article is that the researchers found that subjects with higher plasma leptin and lower ghrelin levels before dieting were the subjects that were more prone to regaining weight after they shed those pounds through dieting. Personally, I thought that the higher the ghrelin levels prior to dieting would cause the subject to be more prone to weight regain, but that’s not the case here, but that’s science. The article goes on to explain that this can be useful information and that these hormone levels can be proposed as biomarkers for predicting obesity-treatment outcomes.

In conclusion we know that virtually everyone produces ghrelin and leptin in there bodies and that these two hormones play a big role in regulating our appetite. Some of us are lucky enough to sustain the proper balance of these hormones, based solely on our genetics, for body weight maintenance. Although, others aren’t so lucky to possess such a talent. Just because someone is lean and skinny doesn’t mean that they are necessarily healthy, and just because someone totes around more body weight than others doesn’t mean that that person is necessarily unhealthy. In closing, all I have to say is that eating right and exercising is a big part of being healthy and maintaining weight despite what these pesky hormones are doing to our appetite. So, to everyone, eat healthy and exercise!

Shedding Light on Alcoholism October 15, 2010

Posted by wframe488 in Behavior, Biology.
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Alcohol

Scientists today are investigating the relationships between stress and the over use of alcohol.  Alcoholism has been an ongoing problem since the Egyptians discovered wine 10,000 years ago. According to the Department of Psychopharmacology, at the University of Heidelberg, in Germany, alcohol consumption is an essential part of daily life of many different societies. The benefits that come from the production, sale, and use of these alcoholic beverages have been found to be detrimental to these societies. The World Health Organization ranks alcohol as one of the primary causes of disease and health problems in industrialized countries.

Alcoholism is an addictive behavior that arises from molecular physiology, according to Sillaber, “Alcohol-related diseases, especially alcoholism, are the result of cumulative responses to alcohol exposure, the genetic make-up of an individual, and the environmental perturbations over time”. In 2002 Sillaber and his colleagues published a scientific paper titled “Enhanced and Delayed Stress-Induced Alcohol Drinking in Mice Lacking Functional CRH1 Receptors. With this study they found that there is a relationship between stress and drinking alcohol for the average mouse. They studied corticotropin-releasing hormone (CRH) and how it mediates responses to stress and alcohol intake. What I want to know is why on earth these mice are drinking alcohol? …but anyway, mice that lacked an efficient CRH1 receptor underwent progressive alcohol intake. With repeated stress added to the mice this particular drinking behavior persisted throughout their life. They discovered that this behavior was associated with the up-regulation of N-methyl-D-aspartate receptor (NMDA) subunit (NR2B).  So, alterations of the CRH1 receptor and changes in NR2B subunits could compose a genetic risk factor for alcoholism.  

Hypothalamus-Pituitary-Adrenal (HPA) axis

Cortisol is a steroid hormone or glucocorticoid produced by the adrenal gland. It is released in response to stress, and low levels of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis, suppress the immune system, and aid in fat, protein, and carbohydrate metabolism.  The secretion of corticotropin-releasing hormone (CRH) by the hypothalamus triggers pituitary secretion of adrenal corticotrophic hormone (ACTH); ACTH is carried by the blood to the adrenal cortex where it triggers glucocorticoid secretion. It’s a long and confusing process but in the end cortisol should be released. In the study by Sillaber the CRH1 receptors of the mice were ineffective which meant that the pituitary gland was not being stimulated to produce the glucocorticoid, cortisol, to deal with the stressful environment. This then lead to excessive alcohol consumption by the mice. This idea sheds light on a possible influence in humans.

Let’s face it we are all stressed at one point or another and we all have different ways of dealing with this stress. Some go fishing, others listen to music, or exercise, but some of us drink alcohol… and lots of it. According to the results of the Sillaber study it is possible that CRH deficiency could be a factor in human alcoholism. Check out the blog by my friend Joe for additional information.